The invention relates to a method for axial correction in a processing machine and a corresponding processing machine, a corresponding computer program, and a corresponding computer program product.
Although the discussion below will concentrate chiefly on printing machines, the invention is not limited to them, but is instead intended for all types of processing machines with driven and non-driven axles and rolls. In particular, the invention can be used in printing machines such as newspaper printing machines, commercial printing machines, rotogravure printing machines, packaging printing machines, or security paper printing machines as well as in processing machines such as bag machines, envelope machines, or packaging machines.
In processing machines, in particular printing machines, a product web is conveyed along by driven axles (web transport axles) such as draw rolls or advancing rolls and non-driven axles such as deflecting rolls, guide rolls, or cooling rolls. The product web, which can be composed of paper, fabric, cardboard, plastic, metal, or rubber and can be embodied in sheet form, etc., is simultaneously processed, e.g. printed, stamped, cut, folded, etc., usually by means of likewise driven processing axles. The driven axles influence the web tension and the stretching of the product web, which is usually controllable, and provide for the transport of the product web via the non-driven axles.
The driven axles include the infeed unit and outfeed unit as well as driven processing axles, for example printing cylinders. These rolls influence the adjustment of the web tension and the register, e.g. color register. The non-driven axles perform the function of web guidance and are driven indirectly by means of the product web. The moment of friction of these non-driven rolls influences the web tension and results in a stationary register error between the individual processing axles.
In conventional processing machines, it is usual to work with external register controls.
In an acceleration or deceleration phase (rotation speed change), a dynamic force must be used in order to accelerate or decelerate the non-driven axles. This requires application of the friction and moment of inertia of the non-driven rolls. During the acceleration phase, the web tension decreases in the web transport direction before the non-driven axle and after it, increases again until reaching the next driven axle. These occurrences influence the web tension and stretching, and thus the baseline alignment of the product web processing.
In the prior art, occurrences of acceleration and deceleration are only taken into account to a small degree in the regulation of web tension and register, e.g. by taking into account a permanently stored run-up curve of the processing axles or by taking into account permanently stored constant changes in web tension set point values.
These measures have the disadvantage that with the occurrence of accelerations, errors in the register and in the web tension are taken into account based not on the current acceleration value, but on a permanently stored one, thus requiring correction of all errors that occur as a regulating difference of a web tension regulator or a register regulator.